R Under development (unstable) (2023-11-16 r85542 ucrt) -- "Unsuffered Consequences"
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> library("R.utils")
Loading required package: R.oo
Loading required package: R.methodsS3
R.methodsS3 v1.8.2 (2022-06-13 22:00:14 UTC) successfully loaded. See ?R.methodsS3 for help.
R.oo v1.25.0 (2022-06-12 02:20:02 UTC) successfully loaded. See ?R.oo for help.

Attaching package: 'R.oo'

The following object is masked from 'package:R.methodsS3':

    throw

The following objects are masked from 'package:methods':

    getClasses, getMethods

The following objects are masked from 'package:base':

    attach, detach, load, save

R.utils v2.12.3 successfully loaded. See ?R.utils for help.

Attaching package: 'R.utils'

The following object is masked from 'package:utils':

    timestamp

The following objects are masked from 'package:base':

    cat, commandArgs, getOption, isOpen, nullfile, parse, warnings

> 
> # Get variable 'a' if it exists, otherwise return the default value.
> value <- eget("a", default=42L)
> print(value) # 42L
[1] 42
> 
> # Short version doing the same
> value <- eget(a=42L)
> print(value) # 42L
[1] 42
> 
> # Same, but look for the variable in 'envir' (here a list)
> value <- eget("a", default=42L, envir=list(a=1))
> print(value) # 1L
[1] 1
> 
> # Get variable 'n', which defaults to command-line argument
> # 'n' ('-n' or '--n'), which in turn defaults to 42L.
> value <- eget(n=cmdArg(n=42L))
> print(value)
[1] 42
> 
> # Equivalently.
> value <- ecget(n=42L)
> print(value)
[1] 42
> 
> proc.time()
   user  system elapsed 
   0.37    0.03    0.39